The increasing speed, complexity, and density of digital circuits increase the power they consume. When a digital circuit is turned on, it constantly consumes power even when it is in a quiescent state. Further, the temperature of the environment can affect the amount of power that the digital circuit consumes. In this regard, efficiency typically varies inversely with temperature causing a digital circuit to generally consume more power as temperature increases.
In addition, the decreasing feature size of digital circuits causes high static leakage currents. A subtle core voltage swing at a low voltage, for example from 1 Volt to 1.05 Volts, can create a dramatic increase in quiescent current, and it is generally desirable to keep the core voltage as low as possible.
Indeed, circuit designers typically select the lowest core voltage that is consistent with the speed requirements of the digital circuit being designed. In this regard, the speed of digital logic varies with voltage and temperature, and in selecting the core voltage, a margin of error is used to ensure that adequate speed is maintained across a wide range of temperature conditions resulting in a core voltage that is higher than what is actually required for many conditions. Accordingly, during operation, the chip often consumes more power and generates more heat than what is actually required.